Behaviors of impurity elements Ca and Fe in vanadium-bearing stone coal during roasting and its control measure

• The behaviors of impurity elements Ca and Fe during roasting were investigated.
• Ca gains ascendancy over Na in competition of combining with vanadium.
• Ca reacts with quartz and albite to generate amorphous phase.
• Fe does not combine with vanadium and not react with other phases.
• A control measure was proposed to reduce negative effect of impurity elements.

The behaviors of impurity elements Ca and Fe in vanadium-bearing stone coal during roasting were investigated in two aspects: combining with vanadium and reacting with other phases. As compared to Na, Ca was more easily combined with vanadium generating water-insoluble calcium-bearing vanadate during roasting. The phase distribution calculated by FactSage showed that Ca reacted with quartz and albite to form amorphous phases, resulting in the entrapment of vanadium, thereby decreasing vanadium recovery markedly. In contrast, Fe in stone coal did not affect vanadium recovery as it did not combine with vanadium and not react with other phases during roasting. In order to decrease the negative effects derived from the impurity elements such as Ca, a control measure of concentrating vanadium and reducing impurities treatment was carried out to decrease the dosage of Na2SO4 and improve vanadium recovery.